The present invention relates to a main helicopter rotor.
In particular, the present invention relates to a rotor of the type comprising a drive shaft designed to turn about is axis; a hub; first connecting means between the drive shaft and hub, for rotating the hub together with the drive shaft about said axis, and enabling the hub to rock about a point along said axis; a number of blades extending substantially radially outwards from the hub and each comprising a connecting device for connection to the hub; a pitch change device connected to said connecting devices; and second means for connecting each said connecting device to the hub.
Known rotors of the aforementioned type are generally referred to as "spherical" rotors.
In the case of a spherical rotor, said first connecting means must be designed to enable torque transmission between the drive shaft and hub; to transmit lift and shear in the rotor plane to the drive shaft, and simultaneously enable the hub to rock about a point along the drive shaft axis, while at the same time generating an appropriate control moment; and to ensure homokinetic transmission between the drive shaft and hub regardless of the rocking position of the hub in relation to the drive shaft.
On known spherical rotors, the above somewhat conflicting requirements are at least partially met by employing a large number of dedicated components. For example, lift and shear transmission between the hub and drive shaft and the rocking movement of the hub in relation to the drive shaft are usually made possible by connecting the hub to the drive shaft via a central spherical joint. Torque, on the other hand, is transmitted by means of links and/or a membrane which, despite also providing for generating the control moments and ensuring homokinetic transmission, is incapable of supporting the blades when the rotor is idle, thus requiring the use of mobile supporting members of the type normally employed on articulated rotors.
In other words, known spherical rotors may safely be said to present a highly complex structure, in terms of both mechanical design and operation, thus resulting in serious drawbacks in terms of cost and safety.